Octocorals are common throughout the Indo-Pacific reefs and play an important role in the ecology of the ecosystem, yet they remain dramatically understudied. The seminar will deal with octocorals of the family Xeniidae, a highly abundant component of Indo-Pacific coral reefs, particularly in the Red Sea. Aspects concerning their life history and acquisition of symbiotic algae (zooxanthellae) at early ontogenetic stages will be addressed. Opportunistic Xeniidae are taking over degraded reefs but taxonomic difficulties force researchers to recognize them as a group whichprecludes detailed understanding of the reef environment and processes on impacted reefs by genera or even species. Our ongoing project deals with phylogeny of the family including provision of species identifications based on their morphological characters. Recent findings reveal that novel microstructural features of their sclerites might be critically important in resolving taxonomic difficulties. Such a study requires introduction of high resolution scanning electron microscopy at magnifications never used before by octocoral taxonomists. Insights on microstructural features of xeniid sclerites also enabled us to examine the effect of ocean acidification on these octocorals and understand the possible function of their living tissue in protection against deteriorating effects of acidic conditions. It is anticipated that studies on xeniids will facilitate future surveys aimed at the maintenance and greater understanding of coral reef diversity and reef-environment function and sustainability.

Polyembryony – the production of multiple genetically identical embryos from a single fertilised egg – is a seemingly paradoxical combination of contrasting reproductive modes that has evolved numerous times and persists in a diverse range of taxa including rust fungi, algae, plants and animals. Polyembryony is thought to characterise an entire order of bryozoans, the Cyclostomata. A molecular genetic approach was used to confirm this widely cited inference, based on early microscopy, and to test the apparently paradoxical nature of this reproductive mode in relation to cyclostomes, and will be reported here. Additional research, also presented here, has revealed further insights into the mating systems of this relatively understudied group of hermaphroditic colonial invertebrates. Mating trials indicated a greater degree of female investment in the presence of allosperm in Tubulipora plumosa and produced evidence of separate-sex colonies in Filicrisia geniculata. If not a complete transition to gonochorism, the situation in F. geniculata indicates at least very pronounced gender specialisation. Further investigations into mating systems of this group may reveal more examples, with implications for our understanding of hermaphroditism and its related traits.